Coating composition of an aromatic polysulfone resin, an epoxy resin, and n-cyclohexyl toluene sulfonamide

ABSTRACT

The novel coating composition is a mixture of an aromatic polysulfone resin and an epoxy resin and is useful as an adhesive and as a protective coating composition for wood, metal, wire, glass and plastics; finishes of the novel composition have excellent stain resistance, good thermal stability, scratch, mar and impact resistance and are useful as an appliance finish, a vending machine finish and an industrial equipment finish.

United States Patent [191 Vasta COATING COMPOSITION OF AN AROMATIC POLYSULFONE RESIN, AN EPOXY RESIN, AND N-CYCLOI-IEXYL TOLUENE SULFONAMIDE Inventor: Joseph A. Vasta, Woodbury, NJ.

Assignee: E. I. duPont de Nemours and Company, Wilmington, Del.

Filed: Mar. 13, 1973 Appl. No.: 340,847

US. Cl 161/185, ll7/232, 161/186, 260/30.8 R, 260/830 S Int. Cl C08g 51/04 Field of Search 260/830 S, 30.8 R; 161/185, 186; 117/232 References Cited UNlTED STATES PATENTS 9/l970 Hayes et al. 260/830 S X June 25, 1974 OTHER PUBLICATIONS G. G. Hawley, ed., The Condensed Chemical Dictionary, 8th edition, (1971), p. 254.

Primary Examiner-Allan Lieberman Assistant Examiner-S. M. Person 5 7] ABSTRACT The novel coating composition is a mixture of an aromatic polysulfone resin and an epoxy resin and is use- 8 Claims, N0 Drawings 1 COATING COMPOSITION OF AN AROMATIC POLYSULFONE RESIN, AN EPOXY RESIN, AND N-CYCLOHEXYL TOLUENE SULFONAMIDE BACKGROUND OF THE INVENTION This invention relates to a coating composition, and in particular, to a coating composition of a polysulfone and an epoxy resin.

Appliances such as stoves, electrical motors, and industrial equipment require heat resistant finishes that are durable, flexible and scratch resistant and have a good appearance. Coatings of aromatic polysulfone resins have good thermal stability but it has not been possible to prepare glossy, flexible finishes from these resins. Typically useful polysulfone resins are shown by Vogel U.S. Pat. No. 3,321,449, issued May 23, 1967; DAlessandro U.S. Pat. No. 3,355,272, issued Nov. 28, 1967; Cohen et al. U.S. Pat. No. 3,518,235, issued June 30, 1970; Pietrusza et al. U.S. Pat. No. 3,536,665, issued Oct. 27, 1970. Epoxy resins are well known in the art and have been widely used in adhesive, paints and the like. A tough, durable, scratch resistant finish .is required by industry today for applications which also require the finish to have excellent thermal stability. The novel coating composition of this invention has these aforementioned properties and also has excellent adhesion to all types of substrates and forms a high quality finish.

The novel coating composition of this invention utilizes an epoxy resin with the polysulfone resin to form a thermally stable finish that is tough, durable and scratch resistant and has excellent adhesion to all types of primed and unprimed metal substrates. Furthermore, the finish has a glossy, high quality appearance which makes the finish particularly useful for appliances such as stoves and refrigerators.

SUMMARY OF THE INVENTION 7' where R is an alkylene group having l-6 carbon atorns and n is from 50-120; and correspondingly;

2. 1-15 percent by weight, based on the weight of the polymer blend, of an epoxy resin of the formula C Cl-I:

where m is a positive integer sufficiently large to give an epoxide equivalent* of to 2,500 and R is an alkylene group of l-4 carbon atoms. The epoxide equivalent of the epoxy resin is the grams of resin that contain 1 gram equivalent of epoxide.

DESCRIPTION OF THE INVENTION The novel coating composition of this invention preferably contains about 10-40 percent by weight of the binder of a film-forming polymer blend. The composition can be pigmented in a pigment to binder ratio of about 1:100 to about 200:100. Preferably, the novel coating composition of this invention has as the filmforming blend 91-97 percent by weight of the polysulfone resin, and correspondingly, 3-9 percent by weight of the epoxy resin.

The polysulfone resin used in the novel composition of this invention has repeating units of the formula where R is an alkylene group of 1-6 carbon atoms and n is from 50-120. In one preferred polysulfone resin of the type that forms a high quality composition, R is and n is from 50-80. This preferred resin can be prepared according to Example 1 of the above D'A- lessandro U.S. Pat. No. 3,355,272.

The epoxy resins that are utilized in the novel coating composition of this invention are the reaction products of bisphenol and epichlorohydrin and having the following structural formula where R is an alkylene radical having I- l carbon atoms and m isa positive integer sufficiently large to provide an epoxide equivalent of 180 to 2,500. Preferably, R is either CH or CHa and the epoxide equivalent is 180-1,025.

One preferred epoxy resin is the reaction product of epichlorohydrin and bisphenol A which provies a resin in which R is isopropylidine. This particular epoxy resin gives a finish with desirable physical properties such as toughness and durability.

Another very useful epoxy resin that gives a quality finish is'the reaction product of epichlorohydrin and bisphenol F which provides a resin in which R is methylene.

Up to 14 percent by weight, based on the weight of the polymer blend, of an aromatic polysulfonamide can be utilized in the novel coating composition of this invention to provide a finish with a slippery surface and that has release properties. Preferably, 4-10 percentby weight of the aromatic polysulfonamide is used to form this composition. The aromatic sulfonamide is of the general formula R SO,-NH-R wherein R is a monovalent aromatic radical and R is either hydrogen, a monovalent cycloaliphatic radical or an alkyl group having 1-18 carbon atoms. Typical resins are for example:

para toluene sulfonamide,

N-methyl para toluene sulfonamide,

N-ethyl para toluene sulfonamide,

N-propyl para toluene sulfonamide,

N-butyl para toluene sulfonamide,

N-hexyl para toluene sulfonamide,

N-octyl para toluene sulfonamide,

N-nonyl para toluene sulfonamide,

N-dodecyl para toluene sulfonamide,

N-lauryl para toluene sulfonamide,

N-tridecyl para toluene sulfonamide,

N-quadra decyl para toluene sulfonamide,

N-stearyl para toluene sulfonamide,

benzene sulfonamidc,

naphthalene sulfonamide,

N-cyclohexyl toluene sulfonamide, and the like.

One particularly preferred aromatic sulfonamide that forms a finish with excellent properties is N-cyclohexyl toluene sulfonamide.

One preferred composition of this type contains 85-95 percent weight of the polysulfone resin, 1-5 percent by weight of the epoxy resin and 4-10 percent weight of aromatic polysulfonamide resin.

The novel composition is prepared by mixing the polysulfone resin and the epoxy resin in a conventional solvent or a blend of solvents. Another method is to prepare a solution of the polysulfone resin and a solution of the epoxy resin and then blend the solutions together to form the novel composition. The other aforementioned constituents can then be added or all of the constituents can be added and blended in one step.

The following are typical solvents that are useful in preparing the novel composition: methylene chloride, trichloroethylene, cyclohexanone, chloroform, chlorobenzene, tetrachloroethylene, l ,l ,'2,2- tetrachloroethane, xylene, N-methyl pyrrolidone, dimethyl forrnamide, dimethyl acetamide, isophorone and other hydrocarbon solvents.

The novel coating composition of this invention can be pigmented as indicated above. Pigments can be blended with the novel composition and then ground by conventional techniques, such as sand milling, pebble milling or ball milling to uniformly disperse the pigment in the composition. Preferably, the pigment is formed into a mill base by grinding the pigment with either a solution of the polysulfone resin or a solution of the epoxy resin or a solution of both of the above resins. Preferably, the epoxy resin is used to prepare the mill base. The mill base is then blended with the novel composition.

The following are examples of the great variety of pigments which can be used in the novel coating composition of this invention: metallic oxides, preferably titanium dioxide, zinc oxide, and the like, metal hydroxides, metal flakes, metal powders, sulfides, sulfate, carbonates, carbon black, silica, silicates, hydrophobic silicates, such as silicone treated with silicone dioxide,

talc, china clay, iron oxide, iron blues, organic reds, maroons and other organic dyes and lakes.

Conventional plasticizers such as butylbenzyl phthalate can be used in the novel composition in amounts of 1-10 percent by weight.

The novel compositions of this invention can be applied to a variety of substrates, for example, metal, glass or plastics by any of the usual application methods, such as spraying, electrostatic spraying, dipping, brushing, flow coating, roller coating, reverse roller coating, coil coating and the like. These coatings are baked at about -400 C. for about 5 minutes to 2 hours. The resulting coating is about O.l5 mils thick and preferably, 1-3 mils thick.

The novel coating composition of this invention has excellent adhesion to bare or treated metals or to metals which have been previously primed or painted with alkyd, epoxy or acrylic enamels. Also, the novel composition can be a highly pigmented coating or can be used as a clear coating.

Finishes of the novel composition have particularly excellent physical properties such as good electrical properties, stain resistance, water repellency, excellent adhesion to primed and unprimed metal substrates, toughness, hardness, crack and mm resistance. The composition is particularly useful as a wire enamel, as a coating for range parts, plumbing fixtures such as sinks, and as a clear coating for hardware items, such as saws, chisels, planes, knives, as a coating for films, such as polyester films to improve electrical and thermal properties. Also, the coating composition can be utilized as a primary finish for refrigerators, stoves, washers, dryers and the like. The novel composition can be used to form structural bonds by coating both sides of interlocking structural members and heating to form the bond.

The novel composition can also be used as an adhesive for metals, glass and high temperature resistant plastics and can be used to form laminates for example of metal to plastic or to fiberglas reinforced plastics. Also the novel composition can be used an an impregnant for a variety of fibrous sheet structures for example, circuit boards can be formed by impregnating and laminating together fiberglas sheets with the novel composition of this invention. The printed metal foil circuit can be laminated to a circuit board using the novel composition of this invention.

The following Examples illustrate this invention. The parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 A coating composition is prepared by blending the following ingredients:

Parts By Weight Polysulfone resin solution (20% solids in cyclohexanone of a polysulfone of the formula where n is from 50-80 a 100.0 I The above ingredients are blended together and then EPOXY resin (having followmg charge into a sand mill and ground to form a uniform structural formula pigment dispersion. I on, I on, /o\ GH 1I-CHz0-@-OCIICHCHOOCHz-CH-CH1 L 5H, ('.)H Jm,

where n is integer sufficiently W 1.0 large to provide the resin with an epoxide equivalent of 180mm together the following ingredients.

By are 'IJ'i'rTW riBTyEIbXZhZ-AWW T W w above 104-2 siloxane resin solution (2% solids in g g fi fi i (prepared above) 2 8 methyl pyrrolidone where the resin I gg gc p a A 8 has a viscosity 0720,000 centistokes) T I 022.8 Hyflqgirwhggjolvem having a boiling ota V point of 182 219 C. T62 Total 0.0

The above ingredients are thoroughly blended together to form a coating composition. A 10 mil thick The above coating composition is reduced to a spray coating is applied to an aluminum substrate with a docviscosity and sprayed onto phosphatized steel panels tor blade and baked for 30 minutes at 200 C. The reand baked for 60 minutes at 275 C. The resulting finsulting coating is clear, tough, scratch and abrasion reish has a 60 gloss of 89 and a 20 gloss of 36. The finish sistant and has good thermal stability. is flexible and will withstand a right angle bend without cracking, The finish also is resistant to solvents such as EXAMPLE 2 methylethyl ketone. A coating composition is prepared as follows: Th invention claimed is:

Pans l. A coating composition comprising 5-60 percent W 7 MT. weigh, by weight of a binder of a polymer blend and a solvent polysulfone res"! 50min" 20% whdsfifl for the polymer blend; wherein the polymer blend concyclohexanone of the polysulfone resin described in Example I) 250 slsts essefltlally of ipg y f g gi g g g r n 25 1. 85-95 percent by weight; based on the weight of -y y V aml ouio (50% Solids in Edge-mtg of the polymer blend, of a polysulfone resin of the Total formula T'Habo'v constituents are thoroughly blended towhere n is from 50- 80;

gether to form a coating composition. 40 2. 4-10 percent by weight based on the weight of of The above coating composition is applied by a doctor the polymer blend, of N-cyclohexyl toluene sulfonblade to separate steel panels having a phosphatized amide; surface and the panels are baked at 200 C. for 30 min- 3. 1-5 percent by weight, based on the weight of the utes. Each of the panels has a tough, durable, scratch polymer blend, of an epoxy resinof the formula resistant and thermal resistant coating.

O CH: EXAMPLE 3 CQCMPEO t HHP A polysulfone resin solution is prepared as follows: L 6

CH3 0 Y oH-om 0--b-@-oom-ccm. .T. Weight g) I Polysulfone resin (described In Example l) 100 H m CH;

C yclohexanone 400 5 where m" is a positive integer surficiem'ia idvtzre an epoxide equivalent of ISO-1,025.

2. An article comprising a metal substrate having at least one side coated with 0.1-5 mils of a dried coalesced layer of the coating composition of claim 1.

3. The article of claim 2 in which the metal substrate is an electrical conductor.

The above ingredients are charged into a reflux condenser and heated to reflux and held at 130-l35 C. for about 8 hours.

A white mill base is then prepared as follows:

w g 4. The article of claim 2 in which the metal substrate Titanium dioxide pjgment 480 is lu n I gg g s g g zg g fi E 3 5 5. An article comprising a flberglas sheet impreg- 450 550) so nated with the dried coalesced composition of claim 1. lsophorone H I 1 6. The article of claim 5 having in superimposed adg fgi' f 'l f I 30 herence therewith an electrically conductive metal Total w sheet.

7 8 7. A laminate comprising at least two sheets of metal 8. A laminate comprising at least two sheets of a heat being firmly adhered together with a dried coalesced resistant plastic being firmly adhered together with a layer of the composition of claim 1. dried coalesced layer of the composition of claim 1. M" V "la-"i l= 

2. 4-10 percent by weight based on the weight of of the polymer blend, of N-cyclohexyl toluene sulfonamide;
 2. An article comprising a metal substrate having at least one side coated with 0.1-5 mils of a dried coalesced layer of the coating composition of claim
 1. 3. 1-5 percent by weight, based on the weight of the polymer blend, of an epoxy resin of the formula
 3. The article of claim 2 in which the metal substrate is an electrical conductor.
 4. The article of claim 2 in which the metal substrate is aluminum.
 5. An article comprising a fiberglas sheet impregnated with the dried coalesced composition of claim
 1. 6. The article of claim 5 having in superimposed adherence therewith an electrically conductive metal sheet.
 7. A laminate comprising at least two sheets of metal being firmly adhered together with a dried coalesced layer of the composition of claim
 1. 8. A laminate comprising at least two sheets of a heat resistant plastic being firmly adhered together with a dried coalesced layer of the composition of claim
 1. 